Mounting Both Gtr Afm's After The Turbos

[a31lunacy]

well after completing my engine conversion (rb26 into cefiro) and running the car up on the dyno (240rwkw on 13psi). i am having some real bad what i believe to be reversion problems the car is running n1 turbos ,r32 gtr ecu remapped, stock injectors, stock afm's. and da da no bov

no im wondering if i can move both the afm's to the inlet piping side or run a single z32 as the car just wont idle after giving it some stick even when free revving it at a stand still it will stall out and run rich i am fouling plugs after not alot of driving and generally it is a bitch to run now before you all tell me to get a plub back bov i wont do it i hate bov with a passion i think they are stupid.

now fab work aint a problem so i want to make up a custom pipe to put the afm internals into im just wondering if i can use both gtr afm's in the same pipe just before the throttle bodys or if i will have to run a single because as you know the gtr afm's measure each turbo separately how does the afm voltage read in the ecu does it measure each signal individually and give an average or does it calculate the two as a distinct voltage and process both numbers as seperate inputs because im sure both afms would read differently

any help would be great

[Adriano]

Is there a reason you dont want a bov, that will be the cause of the issues.

[a31lunacy]

i dont want to use a bov mate sorry with everything that is going on with all the crashes in sa i dont need anything that will let a cop slap a defect on my car and doing it plumb back will be a hassle and i dont believe in reversion killing turbos it aint a proven science just hearsay

ive heard good things about the above method on sr and rb engines that run the single afm but nothing about gtr so that is why im asking

[UWISSH!]

y dont u just use stock gtr BOV's? they dont make noise and are proven to be sum of the best.

also there would be less hassle in doing a plumb back BOV then mounting both the afm's how u wana do it

[Adriano]

To gain a significant advantage in resolving the problem you are having, the afm's have to be after the intercooler, as the air still bounces in the hot pipes. YOu will almost certainly have to make metal housings for the afm's if you want to run serious boost, as the housings crack. IMHO doing a plumback setup will be far less work and less likely to get you a defect..

[Deano45]

I take it that you have had the car engineered with the new engine, otherwise that's a big defect in itself. If that's the case get the blow off valve engineered too. If you don't have it engineered then you have more to worry about then having a cop slap a defect on you for a blow off valve.

If you make up custom housings for the AFM's they need to be the same inside diameter for the resolution to be the same, so take this into consideration.

Other Option would be to change the ecu to one that supports a MAP sensor.

[paulr33]

the car will stall %100 if you have atmo setup, no bov's i dont think would make it stall, but would certainly piss it off and make it grumpy idle

before you go moving the afms - check, are you using the accordian style pipework for the AFMs or have you replaced it?

the accordian style pipework usually avoids the reversion issues, so check you have the accordian pipes as inlet ducts

if you have nice straight, shiny, copper ducting etc then this wont help. a quick test is to try the AFM's open mouted, that is, no ducting in front of them

this will prove if your pipework is the culprit or not (assuming you have changed it)

[a31lunacy]

I take it that you have had the car engineered with the new engine, otherwise that's a big defect in itself. If that's the case get the blow off valve engineered too. If you don't have it engineered then you have more to worry about then having a cop slap a defect on you for a blow off valve.

If you make up custom housings for the AFM's they need to be the same inside diameter for the resolution to be the same, so take this into consideration.

Other Option would be to change the ecu to one that supports a MAP sensor.

yeah its legal we dont really have engineering in sa it had an rb25 in it before hand as my car is an 88 i can get away with a fair bit all i have to do is show regency the engine numbers because im already running gtr brakes all round, i am considering a map sensor driven ecu cause this is bugging me but then its instant defect at least with the stock ecu its all legal and easy too clear at inspection

cant get bov engineered no matter what you do here this is what i call the backward state when it comes to cars so im really cautious with my mods so they will need to be 65 mm housings correct why cant they be bigger please elaborate

the car will stall %100 if you have atmo setup, no bov's i dont think would make it stall, but would certainly piss it off and make it grumpy idle

before you go moving the afms - check, are you using the accordian style pipework for the AFMs or have you replaced it?

the accordian style pipework usually avoids the reversion issues, so check you have the accordian pipes as inlet ducts

if you have nice straight, shiny, copper ducting etc then this wont help. a quick test is to try the AFM's open mouted, that is, no ducting in front of them

this will prove if your pipework is the culprit or not (assuming you have changed it)

can you tell me more about testing are you saying hold the afm slightly away from the pipes and see if it still stalls out whilst free revving ???

i have the rubber piping for the rear turbo but the front has had a pipe made up welded on to the turbo snout because i was at a premium for space under there and eventually i will make rear rubber one outta alloy and the front redirected to the spare cooler pipe hole for a bit of cold air want to make a airbox as well.

now all these suggestions are valued don't get me wrong but i would like to get an answer to my question can both be mounted after the turbos in the same pipe or do they have to read the values for each turbos induction separately

i am going to give this a shot and need some info on it as a search doesn't really have much in the way of gtr only gtst

[paulr33]

sorry maybe i worded it a bit wrong

we've seen users who remove the factory accordian style pipework (which goes in front of the AFM) to the airfilters (pods etc or airbox) cause issues

the accordian pipework helps break the air up somehow when its ducted to the AFM and it gives a clean signal

if you remove the accordian vanes - that is, say you install your own custom 3" pipework to the AFMs (a lot of guys do) and its nice and smooth, curved and no accordian

then the signal the AFM gets reversion, so i think (again, can only speculate what the AFM does) is, it reverberates the signal, and it gives a whacko reading to the ECU

tihs in turn, makes the car run like ass - as the AFMs are saying "hey theres TONS of air coming through" when in reality, its normal levels

this might not be related to the 1st guys post, but its another cause of "reversion" = running like ass / stalling we have seen when messing around with the factory intake / turbocharger setup

[a31lunacy]

yeah it is def reversion causing it to run like this but like i said i want to do a custom piping/airbox setup eventually so kinda rules out using the stock rubber piping but yeah paulr33 do you know if i can move the afm ???

[GT-RZ]

yeah its legal we dont really have engineering in sa it had an rb25 in it before hand as my car is an 88 i can get away with a fair bit all i have to do is show regency the engine numbers because im already running gtr brakes all round, i am considering a map sensor driven ecu cause this is bugging me but then its instant defect at least with the stock ecu its all legal and easy too clear at inspection

cant get bov engineered no matter what you do here this is what i call the backward state when it comes to cars so im really cautious with my mods so they will need to be 65 mm housings correct why cant they be bigger please elaborate

can you tell me more about testing are you saying hold the afm slightly away from the pipes and see if it still stalls out whilst free revving ???

i have the rubber piping for the rear turbo but the front has had a pipe made up welded on to the turbo snout because i was at a premium for space under there and eventually i will make rear rubber one outta alloy and the front redirected to the spare cooler pipe hole for a bit of cold air want to make a airbox as well.

now all these suggestions are valued don't get me wrong but i would like to get an answer to my question can both be mounted after the turbos in the same pipe or do they have to read the values for each turbos induction separately

i am going to give this a shot and need some info on it as a search doesn't really have much in the way of gtr only gtst

hope you got your facts right mate because i was told rb25 would require an engineers cert directly from the regency call centre, aswell as the bigger brakes. so cant see why an RB26 would get the green card?

the only advatnage you will have is that the cops generally don't know the difference between any off them.

[paulr33]

you can move the AFMS but another known work around when you replace the accordian pipework is to place a bend in the ducting

if you look at the HKS ducting kits, in front of the AFM and between the pods, there is usually a bend, the bend is usually enough to break the reversion issue

from memory the reversion only occurs when the ducting is perfectly straight or a slight bend

[a31lunacy]

hope you got your facts right mate because i was told rb25 would require an engineers cert directly from the regency call centre, aswell as the bigger brakes. so cant see why an RB26 would get the green card?

the only advatnage you will have is that the cops generally don't know the difference between any off them.

yeah i got my fatc right too register the car with the rb25 all i had to do was get a statement of modification from regency then do what they said which was bigger brakes( and the usual stuff to get the car reg for the first time) did it got car registered (with an inspection ) got another statement for the rb26 same shit just needed bigger brakes (which i had already) and inspection of change of engine numbers did it car now reg with that engine

i have been through the channels and because my car is 88 it does not go through the same compliancing system and i am free to do these sorts of engine swaps without an engineering report dont ask me why i think its a stupid play on laws but hey better for me yeah

you can move the AFMS but another known work around when you replace the accordian pipework is to place a bend in the ducting

if you look at the HKS ducting kits, in front of the AFM and between the pods, there is usually a bend, the bend is usually enough to break the reversion issue

from memory the reversion only occurs when the ducting is perfectly straight or a slight bend

so both the afms can be moved to the one pipe just before the throttle body just confirming cause i wouldnt want to start then find it dont work.

i might get a spare set of afms and make up a new pipe just incase, yeah i belive the reversion issue can be fixed with that but i want to do a custom airbox and piping so as little in that area the better as there is not alot of room and moving the afms will tidy up the engine bay heaps

if anyone else has anything to add would be great esp if some one has done the mod would like to get some ideas but i will attempt this in the next month or so as it really makes the car un driveable

i think the main cause of this is the lack of bov as the air has no where to flow but back out the piping when the throttle body closes and into the afm's i guess most people that run hard piping also have bov either stock or aftermarket.and im pretty sure reversion can occur with the stock piping as the air has to go some where but mainly when you run no bov. with the stock one/ones in place i guess it wouldnt happen.

[R31Nismoid]

the problem is the stock BOV's leak @ idle, as they are designed. You have removed this, hence its stalling.

Your first post makes a comment about legalities - legally you actually NEED the stock BOV's on there, so i fail to see how it could be illegal.

Either way to get around it as you want your setup, you have to go to the ghetto.

Put a single (meaning, one) AFM AFTER the cooler, and splice the wires and run wires to the other AFM loom.

This will split the signal and make the ECU think you have two AFM's.

Putting two AFM's post intercooler is a bad idea. It will create a lot of turbulence being the air is now in boost/pressure.

Remember though this is going to cause a restriction. GTR plenum and the AFM size are not identical, AFM is SMALLER.

IMO - put the stock GTR BOV's on, alternatively you can always just use ONE GTR BOV, this is also perfectly fine and makes the job a lot easier.

[a31lunacy]

the problem is the stock BOV's leak @ idle, as they are designed. You have removed this, hence its stalling.

Your first post makes a comment about legalities - legally you actually NEED the stock BOV's on there, so i fail to see how it could be illegal.

Either way to get around it as you want your setup, you have to go to the ghetto.

Put a single (meaning, one) AFM AFTER the cooler, and splice the wires and run wires to the other AFM loom.

This will split the signal and make the ECU think you have two AFM's.

Putting two AFM's post intercooler is a bad idea. It will create a lot of turbulence being the air is now in boost/pressure.

Remember though this is going to cause a restriction. GTR plenum and the AFM size are not identical, AFM is SMALLER.

IMO - put the stock GTR BOV's on, alternatively you can always just use ONE GTR BOV, this is also perfectly fine and makes the job a lot easier.

i wont be using the afm and plumbing it inline i will be removing the internals and making a custom pipe to mount it in so i can use the 2 yes?? i think you may have misunderstood how they will be mounted there is no way i would mount two afms one after the other that would not only look stupid but cause a massive restriction to my piping.

so now knowing this can someone answer can i use both the afm internals mounted in a custom pipe to run the car ?????

look at the end of the day i want to try something different if we all did the same mods to cars then the scene would be boring and no fun at all if it works ill be happy ill have a car that is unique and just a bit different to everyone elses if i wanted too i could and would have put a bov on it... imo thats the easy way out

i just hate bov don't ask me why just do lol i remember 6 years ago when i got my first turbo car the first mod was da da a big shiny bov that made a lot of noise never again

[STATUS]

it can be sorted, forget the BOV lovers and plumb back jabber. Are you using nistune? feel free to email me the map and i will have a look at the 'reversion" points and low end map scaling for starters. We dont run bovs on our drift cars as the throttle lag is hard to live with when on and off the throttle rapidly.

secondly you can run a single Z32 post cooler as a last resort.... works fine.

Metal Z32 housing are available off the shelf.

Edited May 31, 2009 by URAS

[Adriano]

Stock bovs arent shiny or noisy. I would be sceptical about saying the car will be legal without one or two, as the stock bov's are an emmission control device, nothiing more. YOu can place a single afm in a pipe twice the surface area of the stock afm after the intercooler, however youi will need to have mesh on both sides of the sensor(as the factory does), adn will need to clean the sensor every month or so. Have a look at my thread in the fabrication section regarding custom afm's

[R31Nismoid]

i wont be using the afm and plumbing it inline i will be removing the internals and making a custom pipe to mount it in so i can use the 2 yes?? i think you may have misunderstood how they will be mounted there is no way i would mount two afms one after the other that would not only look stupid but cause a massive restriction to my piping.

so now knowing this can someone answer can i use both the afm internals mounted in a custom pipe to run the car ?????

No you cant take the internals out, and put them into a different dia pipe.

They are calibrated for the size of the piping they come in. Eg Nismo/Z32 AFM's come in different case sizing, and are slightly different in calibration even though its the same sensor.

Hence i made no refernce to doing so because it can't be done. The only options are as i stated.

i just hate bov don't ask me why just do lol i remember 6 years ago when i got my first turbo car the first mod was da da a big shiny bov that made a lot of noise never

A recirc BOV wont make lots of noise with an airbox, thats why they were made that way so... thats a poor reason